Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
787 FXUS61 KGYX 190502 AFDGYX Area Forecast Discussion National Weather Service Gray ME 102 AM EDT Tue Aug 19 2025 .SYNOPSIS... Cooler weather continues through the middle of this week with a weak trough triggering some showers Wednesday, followed by high pressure building in from the west through Saturday. Temperatures will warm back into the 80s by late week and to start off the upcoming weekend. && .NEAR TERM /THROUGH TODAY/... High pressure remains centered over the Gulf of Maine today which will continue a cool dry flow. Afternoon seabreezes are expected. Skies look to end up more in the partly cloudy range as low pressure approaches from the Great Lakes Region. We will see continued drying at the surface as relative humidity values once again drop to around 35-45% during peak heating. Overall, it will be another fair weather day with high temperatures in the low to mid 70s areawide after any early morning valley fog dissipates. && .SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/... Will start to see cloud cover increase Tuesday night as low pressure moves closer to the region. This keeps temperatures from plummeting like we have seen the past few nights, but it will still be cool with temperatures in the low 50s south of the mountains, and mid- to upper 40s to the north. The 12Z NAMNest and 12Z HRRR suggest showers may be see as early as around sunrise Wednesday morning, but there is still significant uncertainty between them so kept chances low during that time. Most guidance keeps the bulk of precipitation to the south of the forecast area on Wednesday but there are several members that bring some meaningful rain to southern NH. That is where our highest PoPs are, with the rest of the CWA struggling to get wetting rains. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... The main thing to watch in the extended will be increasing wave action from tropical cyclone Erin, which will be passing several hundred miles east of the Gulf of Maine late week. This will likely result in potentially dangerous rip currents and increasing swells. Otherwise, mainly dry weather and near average temperatures look to prevail through Saturday. An approaching frontal boundary early next week looks to bring our greatest potential for some beneficial rainfall. Previously... Once the Wednesday system passes, another period of mostly dry weather is expected from Thursday through Saturday with gradually warming temperatures, although the mountains may see some diurnal showers on Thursday. This dry weather is owed to an upper ridge steadily building toward New England as the latest forecast from NHC has Tropical Cyclone Erin passing well to the south and east of the area as well as any extra moisture that would potentially bring any additional rain chances. However, long- period swells from Erin are modeled to begin arriving from mid to late week, likely bringing high surf to the coast as well as high risk of dangerous rip currents. Highs go from the 70s Thursday to the 80s Friday and Saturday. Global models are in good agreement by shifting the high to the east of the area by Sunday as an upper low digs in north of the Great Lakes and sends a frontal boundary toward New England. Things can always change, but with at this point there is a pretty good signal from ensembles for this front to bring measurable rainfall to portions of the area Sunday or Monday, but amounts are uncertain. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... Short Term...Mainly VFR expected today and tonight other than early morning valley fog. Afternoon seabreezes will allow winds to go onshore midday. Long Term...A low pressure system will bring increasing shower chances on Wednesday into Wednesday night and the potential for IFR to MVFR restrictions. However, confidence in details is low other than it looks like the NH terminals have the higher chances. After this system passes, primarily VFR Thurs-Sat other than the possibility of nighttime valley fog at HIE and LEB. && .MARINE... Short Term...Wind gusts and seas remain below SCA criteria through tonight as high pressure remains centered over the waters. Winds shift northerly tonight, than back to southerly Tuesday afternoon, with gusts falling below 10kts. Long Term...Conditions remain below SCA levels Wednesday. Winds remain below criteria through Friday, but seas will build through late week as long-period swells from Tropical Cyclone Erin (passing well to the south and east of the waters) arrive over the waters Thursday and Friday, likely requiring a Small Craft Advisory. Seas will start to come down over the weekend but could still remain above SCA levels based on the current forecast. Southerly winds may also gust to around 25 kt as the pressure gradient tightens with high pressure to the east and an approaching frontal boundary from the west. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Ekster SHORT TERM...Ekster LONG TERM...Combs/Tubbs